Active pixel sensor array with simple floating gate pixels

An imaging device comprising:

• a monolithic semiconductor integrated circuit substrate;
• a focal plane array of pixel cells formed on said substrate by an integrated circuit process that is compatible with a complementary metal oxide semiconductor (CMOS) process, each one of said pixel cells comprising,
• a photogate electrode overlying said substrate and operable to accumulate photo-generated charge in an underlying photogate portion of said substrate,
• a barrier gate formed on said substrate adjacent said photogate portion, and
• a pixel transistor formed on said substrate and configured to have a first diffusion region adjacent said barrier gate, a gate and a second diffusion region, said gate connected to said photogate electrode to form a floating gate,
• wherein said barrier gate is operable to transfer said photo-generated charge from said underlying photogate portion of said substrate to said first diffusion region of said pixel transistor, and wherein said gate of said pixel transistor produces an electrical signal comprising a signal component indicative of said photo-generated charge and a noise component indicative of noise associated with said pixel;
• and
• MOS image signal processing electronics integrated on said substrate and connected to communicate with said focal plane array and to provide on-chip signal processing of electrical signals from said pixel cells.

An imaging device comprising:

• a monolithic semiconductor integrated circuit substrate;
• a focal plane array of pixel cells formed on said substrate by an integrated circuit process that is compatible with complementary metal oxide semiconductor (CMOS) process, each one of said pixel cells comprising,
• a photogate overlying said substrate and operable to accumulate photo-generated charge in an underlying portion of said substrate,
• a barrier gate formed on said substrate adjacent said photogate, and
• a pixel transistor formed on said substrate and configured to have a drain adjacent said barrier gate, a gate and a source,
• a capacitor having a terminal connected to both said photogate and said gate of said pixel transistor to make said gate of said pixel transistor a floating gate,
• wherein said barrier gate is operable to transfer said photo-generated charge from said underlying portion of said substrate under said photogate to said drain of said pixel transistor which produces an electrical signal having a signal component indicative of said photo-generated charge.

A method, comprising:

• producing charge in a portion of a semiconductor substrate under a photogate electrode in response to incident photons incident to said portion;
• using a transfer gate formed in said substrate next to said photogate to output said charge in said portion;
• using a drain of an output transistor formed in said substrate next to said transfer gate to receive said charge from said portion;
• and
• connecting a gate of said output transistor to said photogate to form a floating gate so as to convert said charge into an electrical signal.